The objective of this project is to develop a Raman based technique for real-time, in situ diagnosis of breast tissue during needle biopsy or surgery. We have previously shown that Raman spectroscopy can be used for in situ histochemical analysis of biological tissue. The first part of this project involves the design of a fiber-optic needle probe capable of delivering and collecting the necessary light to the tissue being studied. The second portion depends on the development of an algorithm for classifying breast tissue based on its Raman spectra. We have already established that the information necessary for disease classification is contained in the Raman spectra. Now we need to determine which chemicals are responsible for these differences in the Raman spectra and develop a decision algorithm. Simultaneously, we are designing an appropriate probe for obtaining in vivo Raman spectra.